A rock of mass 4.5 × 102 g is tied to one end of a string that is 2.1 m in length. Holding the other end above his head, a boy swings the rock around in a circle whose plane is parallel to the ground. a. If the string can withstand a maximum tension of 4.5 N before breaking, what angle to the vertical does the string reach just before breaking? b. At what speed is the rock travelling just as the string breaks?
